不同地表情况下Cooray-Rubinstein算法的应用及其精度检验

将雷电水平电场Cooray-Rubinstein(C-R)算法推广应用于地表电导率垂直分层的情况,并利用时域有限差分(FDTD)方法对不同地表情况下C-R算法的精度进行检验。结果表明,C-R算法的适用条件为:距离回击通道为100~1 000 m、地表电导率介于0.001~0.01 S/m,最大误差小于10%。当土壤电导率均匀分布时,C-R算法的精度最好;对电导率水平分层的情况,当上层电导率小于下层电导率时,C-R算法的精度较优;当电导率垂直分层时,若观测点处的土壤电导率小于闪击点处的电导率时,C-R算法的计算精度较高,反之,精度较低;对任何光滑有耗地表而言,利用C-R算法计算的首次回击水平电场的精度优于继后回击。     

一种结合R树索引和海伦公式的偏航算法

针对卫星导航系统中嵌入式终端常用偏航算法(欧氏距离度量法和缓冲区近似法)的局限性,提出了一种结合R树索引和海伦公式的改进偏航算法。该算法采用R树索引筛选法缩小目标点所在航线范围,结合海伦公式快速计算出目标点到航线的距离,进而做出偏航判断。理论分析和实验结果表明,改进算法实现零误差快速偏航判断,显著提高导航定位终端偏航报警的实时性和准确性,从而降低了对终端计算能力的要求,满足了上万个航路点的快速偏航计算要求。     

平行剖面法用棱柱和截锥公式计算块段体积注意的问题

用平行剖面法计算资源/储量时,若矿体块段在相邻两剖面上均有面积,且控制两面积的工程间距或控制每个剖面面积的工程见矿平均厚度不相等的情况下,使用棱柱体公式计算块段体积,或相邻两剖面上面积形状不相似的情况下,使用截锥体公式计算块段体积,均存在一定的误差。而拟柱体公式则是精确计算块段体积的通用公式,其使用不受上述条件的限制。因此,在这种情况下,建议限制或停止使用棱柱体和截锥体公式,提倡统一使用拟柱体公式来计算矿体块段的体积。     

受控三轴应力-应变下沉积物声速与物理力学性质的关系

对南海某海域深度100～400 m的海底浅层（约2 m埋深范围）沉积物柱状样在接近海底水压力下进行三轴应变-声学同步测量,结果表明沉积物纵波声速有两个特征:（1）从应变过程开始到结束,沉积物纵波声速不断变化;（2）平均声速随着平均静弹性模量的增加,由大变小又由小变大,存在声速最小值。这些结果与海底浅表层沉积物的物理力学性质、围压、颗粒的结合状态改变有关。此外,沉积物动弹性模量和孔隙度呈良好的负相关性,这与孔隙度增大含水量增大有关;动弹性模量是静弹性模量的10～100倍,这主要与三轴应变试验的应变数量级与声波振动产生的应变数量级的差异大有关。采用本论文实验测量的数据分别建立了双复合参数-声速和孔隙度-声速经验公式,分析结果表明双复合参数-声速公式声速预报误差约是孔隙度-声速公式的1/4,表明双复合参数-声速公式更加有效。     

Fracture modes in the Silurian Qusaiba Shale Play,Northern Saudi Arabia and their geomechanical implications

Fracture and in-situ stress studies were conducted for unconventional prospect evaluation in the Silurian Qusaiba Shale, northern Saudi Arabia. Borehole image logs, oriented cores, seismic, and drilling observations were used in the studies. The fractures include natural fractures and induced fractures. The induced fractures were studied to assess the stress regime in terms of directions and magnitudes. The present day maximum horizontal in-situ stress trend varies from NNW-SSE to NNE-SSW, and shows a regional pattern dominated by Arabian plate tectonics. The relative magnitudes of the current day stresses are characteristic of an extensional to strike-slip regime. Natural fractures of microscopic (microfractures) to macroscopic (macrofractures) scales include extension fractures (joints/veins), and faults manifested as shear and hybrid (extensional-shear and compressional-shear) fractures. Joints clustering into zones are rare, unless when associated with fault zones. Over half of the faults (56%) show clustering into fault zones with their widths (thickness) varying by up to 5 orders of magnitude, and lengths and displacements varying by up to 4 orders of magnitudes respectively. The study identified five distinctive, regional, fracture sets: one gently dipping (bedding-parallel or at low angle to bedding) and up to four moderately to steeply dipping fracture sets: an easterly striking set is the oldest, followed by three younger major sets striking NNW-SSE, N-S, and NNE-SSW. The younger fractures are nearly parallel to the present day maximum horizontal in-situ stress. Crack-seal mechanism (natural hydrofracturing) dominates initial fracture growth, some with several phases of partial to complete mineralization or coating, dominated by calcite, quartz, and dolomite. Aqueous and hydrocarbon gaseous and fluid inclusions are common in the fractures' mineral filling. The regional nature of in-situ stresses and natural fractures means their occurrence, orientation, relative dominance, and relative age and relative apertures are easier to predict and manipulate for well planning and completion, including hydrofracturing. Forward modeling shows that natural fracture network are not critically stressed under reservoir conditions but when subjected to massive hydrofracture stimulation they and the bedding discontinuities form the seeds for the growth of a complex hydrofracture network that potentially grows out of presumed stress-barriers. Lack of stress rotation around faults in wells supports the modeling results. Microseismic monitoring gives time-lapse (incremental) microseismic events of two types; random and linear patterns parallel to maximum horizontal in-situ stress and the predominant natural fracture trend. Bulk microseismic cloud has no unique link to fault trends mapped from high resolution borehole images. This finding challenges the usability of uncalibrated microseimic monitoring of massive hydrofracturing to map faults.     

微型钢管-旋喷复合桩在软土区的试验研究

软土地质条件下的既有建筑物地基基础加固或改造面临诸多复杂条件,施工安全和周边环境保护尤为重要,为此提出微型钢管--旋喷复合桩工艺。通过开展微型钢管--旋喷复合桩各项承载力现场试验研究,获取钢管桩应变数据,分析其承载特性及传力机制,总结提出微型钢管--旋喷复合桩承载力设计计算公式,为开展工程应用提供理论依据。     

Appraisal of Budyko formula in calculating long‐term water balance in humid watersheds of southern China

The Budyko formula for estimating the long‐term average annual evaporation is applied to calculate the long‐term water balance in 29 humid watersheds of southern China. As a result of overestimation of evaporation, the long‐term average annual runoff is underestimated, with the Nash‐Sutcliffe efficiency (NSE) at just ? 17%. A one‐variable linear regression model is employed to find that the Budyko scatter and the relative errors of Budyko runoff and evaporation estimates are all closely related to the long‐term aridity index. Through combining the original Budyko formula with the different linear regression models for estimating the Budyko estimation errors, three forms of revised Budyko equation for estimating the long‐term average annual runoff are derived, with all their NSE values to be around 66%. After calibration, both one‐parameter Turc‐Pike and one‐parameter Fu equations lead to the NSE value of 60% in estimating long‐term average annual runoff. Two conclusions are made, with the first one being that, the nonparametric Budyko formula, although very intuitive and very simple, does not apply well in calculating long‐term water balance in 29 humid watersheds in southern China. The second one is that, the parametric evaporation formulae, with locally optimized parameter values, can achieve better accuracy in estimating long‐term average annual evaporation and runoff than the nonparametric Budyko evaporation formula. Copyright © 2011 John Wiley & Sons, Ltd.     

Characteristics and Causes of Changes of Pan Evaporation in China During 1957-2001

Evaporation is an important component of surface heat and water balance, and is affected directly by land use and climate change. This paper studies the changes of evaporation in China associated with the global climate change, and explores characteristics of the corresponding regional water cycle variations. The 20-cm-caliber pan evaporation measurements collected from 427 meteorological stations in China from 1957 to 2001 are analyzed to disclose the small-pan evaporation variation trend in China and the associated causes. The results show that although the annual average temperature over China exhibits an upward tendency of 0.2°C/10 yr for the past 45 years,the pan evaporation on the whole has decreased by －34.12mm/10 yr. Nonetheless, a significant increase of pan evaporation is observed in a few areas such as the northern part of the Greater Hingan Mountains in Northeast China and the Beishan Mountains in Inner Mongolia. The largest decrease of pan evaporation lies in East China, northern parts of Northwest China,South China, and southern Tibet. An analysis of energy balance and aerodynamics using Penman's formula proves that the drop of pan evaporation in East China is mainly due to a significant decline of source energy for evaporation, while that in West China is mostly attributed to an aerodynamic reduction. The analysis on tendencies of various meteorological and other related factors shows that wind speed and sunshine hours are two most important factors causing the pan evaporation reduction in China.     

A probabilistic investigation of infiltration in the vadose zone: proposal for a new formula of infiltration rate

The infiltration rate in the unsaturated zone is analysed from a probabilistic point of view. It is shown that the empirical formulas of Horton and Kostiakov, without apparent physical basis, are explained in a probabilistic approach. Horton's formula reflects a Markovian process contrary to Kostiakov's formula. This approach made it possible to explain why Kostiakov's formula is more powerful than that of Horton. A new equation of infiltration is proposed. The three formulas were compared, for four types of soil, with the model of van Genuchten based on the Richards equation. Copyright © 2006 John Wiley & Sons, Ltd.     

2013年全球发现的新矿物种

对2013年度全球发现并经国际矿物学协会(IMA)新矿物与矿物分类命名专业委员会(CNMNC)批准的137种新矿物资料进行了系统梳理,特别是从矿物名称、晶体化学式、晶系和空间群、晶胞参数、主要粉晶数据、物理性质、光学性质、产地与产状、与其他矿物种的关系、矿物名称来源、化学反应和光谱学特征等方面归纳总结了这些新矿物的重要...